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March 8, 1932. L M FOSTER 1,848,705

PROPELLER WHEEL FOR AIRCRAFT vFiled July l5. 1927 ff/f. w

Patented Mar. ks, 1932 PATENT OFFICE LUCIAN M. FOSTER, OF TROY, NEW YORKPROPELLER WHEEL FOR AIRCRAFT Application ledvJfuly 15, 1927. Serial No.205,950.

This invention relates to a rotary propeller wheel for airships in whicha plurality of relatively thin sheet metal blades are arranged toextendcircumferentially and .spie

' 5 rally around a suitable supporting hub in uniformly spaced relationcircumferentially and concentric with the axis of rotation asdistinguished from thev radially extending wooden blades now in commonuse.

The main object is to obtain a maximum propelling power with a minimumweight of the propeller. l f

Another object is to construct and assemble the blades in such mannerthat all portions thereof will retain substantially their normal formand contour against deflecting, twisting or vibrating strains by impactwith the air, particularly when driven at high speed under heavy load.

A further object is to obtain a maximum area of impact of the bladesagainst the air with a minimum radial width of the blades and at thesame time `to maintain a closer continuity of such impact throughout,the circumferential length ofthe wheel than has heretofore beenpractised by making the impact sides of the blades concave in crosssection and causing yadjacent ends of the blades to approach closely toa radial plane between them so that the air leaving the heel of eachblade will immediately impinge against the toe of the next succeedingblade.

Other objects and uses relating to specific parts of the propeller willbe brought out in the following description. Y

In the drawings Figure lis an end view of a propeller wheel embodyingthe various features of my invention. I

Figure 2 is an enlarged plan of the same propeller.

Figure 3 is an enlarged lengthwise sectional view taken on line 3-3,Figure 1, portions of one of the blades being broken away.

Figure 4L is an enlarged elevation, partly broken away and partly insection, of one of the braces. f

As illustrated, this propeller comprises' a tubular hub -1- havingaxially spaced col 570 lars l-2-.-, each provided with a pair ofdiametrically opposite radial spokes 3- having their outer ends providedwith concave seats 4 adapted to be brazed or otherwise rigidly securedto the convex sides of a pair of propeller blades -6- of concave-convexcross section.

All of the parts of the propeller are preferably made of comparativelythin and light, yet strong and durable non-corrodible metal constructedand assembled in such manner as to reduce the resistance of the air to aminimum when the propeller is rotated.

The tubular shaft -1- is adapted to be connected at either end to asuitable driving shaft as -A- through the medium of separable couplingsections -aso that the same propeller may be used at either end or ateither side or similar propellers at both ends or both sides of theairship.

In fact, the construction of the propeller permits it to be used on anypart of the airship, either in a vertical position for lifting purposesor in a substantially horizontal position for forward driving purposes.

The collars 2 may be welded, brazed or otherwise permanently secured tothe periphery of the tubular hub -1- in axially spaced relationdepending somewhat upon the spiral pitch and circumferential length ofthe blade 6 so that the spokes on both hubs may be disposed insubstantially parallel planes at right angles to the axis of the hub -1-corresponding approximately to the transverse planes of theends of thepropeller blades.

That is, the spokes -3- of each hub 2 are substantially straight andradial, as shown more clearly in Figure l, the outer end of each spokebeing brazed or otherwise secured to the convex side of thecorresponding end of one of the blades while the other Vspoke issimilarly secured to the convex side of the corresponding end of theother blade, the portions of the spokes adjacent the blades beingwidened and comparatively thin and also made concavo-convexlongitudinally to conform to the convexed contour of the adjacentportions of the blades, thereby to afford a relatively broad bearing forthe blades and at the same time reducing to a minimum the air resistanceof the adjacent portions of the spirally around the hub *1-concentricwithV the axis thereof and in planes` intersectingz each othersubstantially midway between the collars Q- so that the oppgsitelendslof each blade will lie in transverse planes substantiallyequaldistances.: axially from #the lplanefof iintersection.. and willalso approach closely to a vmedial plane. p assingv dia-metricallytlhrough :the axis of the: hubv Wherebyiwhen theblades. are .rotated themore orless .compressed air leaving the heel ofeaclr` bladewill:instantly -impinge againstv .theitoeofthe other blade :formaintaining a. substantially .continuouspressureg against the. air aslthe propellenis rotated. t

These blades arez preferably Vmade of thin sheet metalz and,`concavofeonvexV in :cross section:throughout .their -..lengths Vwiththeir convex Isides .securedto the; outer ends ofthe spokes andftheir-concavesides facing f frearwardlyz .for propelling impact Withithe.lair.r A

.f That is,if.the lzcrossisection. of .eachbladeis in the form ofthe arcof a :circle of-.nelatively small radius as .compared's-wit-liftheiradius ofithe: propeller thereby. greatly istiffening all yportions.Voff thel blades'i against 'warpingv or amiahdeflectioinby impact-withitheair andat the sameetimeformingrinzeach blade a'con- .tinuous`channel openj ati. both -ends which; affords-f aenelatiiviely; largeair.. impact. area as icomparedmyith;itsradial@ width. and `causesitherair to s .become l p-Ocketedior. fconfined.-.wthfinithef. crosssectionallimits; .of fthe channel as the propel-ler is rotatedin:thedirectonvindi-- cated lby thearrows. v

Y iltr-isgfound' thatfwhengthis propeller Avis-r.o ftatedfati ftherequiredvelecity: for zecient worlpthe air pressurennjthe channel.surface tot eachfblade. rapflly-nnreasesffromythe toe tothe heel ofthebladereaching-its-maximum pressure atl-the Vheelf andgwhile 'thepeculiar .concave-convex crosssec'tional area and circumferentialVcircularityof-each 4blade ...may underl,gordinary-.1conditions besufficient to 4hold-all portions ofthebladeaganst yielding under thisgradually increasing air. pres,- isureit, may be desirable piuticularlyLunder heavy'loads to use \.braces,as f7 having their innerends connectedtothe .endg of lthe lijnbf adj acentihe concave Vsides of the blades Iand their' outer :ends 'fastened-to the adjacent Set .ef spokes 4:whichvare attached v to the heels of thebllafles; and therebyteassisi;v eachspoke in; holding-the heelslfof the blades where the air pressure isvgreatest, against warping or forward deflection by air pressure.

The inner ends of the braces -7- are provided with internally threadednipp-le sections -7- having their heads engaged in apertured parts ofthe hub and their threadedv portionsV engagedvwith the-f adjacentthreadediends ofi-thamainabodies: of the 1 braceswhich arepreferably made in theform of strong wire andare provided at their outeren'ds-withheads "S-.engaged in apertured 4portionsofthe.outer ends ofthe spokes 3- to which the heels of the blades 6- are secured.V

The nipples 7'- are provided with angular 'outerfeends -..-i7

.iaecessible `Afor thefrecaption of a-wrenchon equivalent tool.wherebylilzhe@ bracesmaywbe tightenedzor loosened fat -w1.-`.QV A

. Y .'Qpemtian Y l' 'WheIr the .propelleiuis4 constructed finfzthemanneri described,l and rfotated' in the direc- Ltion indicated Vbyithearrows the airffwillbe lpicked up by thetoes. ,las 9461-.. of each..blade 'and causedy to ftraveli along-fthe ,spirally .inclin'ed channel.side :thereofV i with 5 gradually increasing pressure sufficient toipropel `the machine Vforwardly until the'4 maximu'mipres- =sure"at; theheel as=...;6fA-sofnthebladezis reached at which time :the airfundervmore; or --less 1 high pressure .-.is` iinstantly. released: and allowedtoimpinge.againsttheltoe ,offthe othfer: bladelito `.travel alongrthejchannel 'thereof with equal force and powenuntil t'hehighlyicompressed airqleaves thezheelffof. thel Second blade. andfimpinges'against .the .toe of .fthe (first. bladenthus';l 5 completing .'thecycle and .equilibrium i ofipressures on;l both fblades. for

K :propelling the: machine forwardly.

il have foll'ndrgthatthe-useot ltwo similar ,bladesfofi nearlysemi-circularffform lcircuniferentially are' bestsuited1forYaircraftpropulsion,

but it is evidentthat-A af"g1eater nu1niber .of bladesoequalcircumferentiialL length 11i-ray; be employed gif?desired,vwithoutfdepartf ing from the spirit of this invention.

Vi. lt will?beinetefithatitheplzopeller; blades f 6- arranged in themanner described-@spirallyand; circumferentially around. the;v axis ,ofthe.` hulnflconstitute what mayf be Y termedI @sectional rrimf ofy.the\wheelginwhi'ch fthe ,sections ofgtherim .travel endwisethrough lgthe, airs about-` .tha axisv of the.v hub-,fas distin guished from theedgewise travel ofthewoodfen fradialbladesicommonly used .thusipermit--tinglthe nseofltheentire area ofthe channeled .sidjes o fgthefi againstthe air as the impelling force for propelling the machine whereas in theordinary wooden radial blade the impact area is limited to a relativelysmall section of the outer end thereof.

Furthermore, by making the rim sections or blades approximatelysemi-circular and arranging them so that their corresponding endsapproach closely to a medial plane passing through the axisl of the. hubestablishes al substantial continuity of impact with the air whichpermits the propeller to be driven at a lower rate of speed than wouldbe possible with the use of radial or other blades with more or lesscircumferentially elongated air gaps between them.

This continuity together with the substantially equal cross sectionalimpact area also produces a substantially balanced end thrust of thepropeller and reduces to a minimum any liability of side thrust socommon in radial blades so that the resultant effect is less wear of thebearings and greater stability of the motion of the machine andconsequently less liability of shattering or disintegration of anyportion of the blades.

While I have shown and described the propeller wheel as adapted to beused more particularly for aircraft, it is evident that the sameprinciple of construction may be used in connection with water craft,ice craft and land craft without departing from the spirit of thisinvention.

What I claim is:

1. An aircraft propeller wheel comprising a hub having a pair ofdiametrically opposite radial spokes arranged in axial spaced relation,a pair of substantially semi-circular concave-convex blades extendingspirally and concentrically about the axis of the hub, the toe ends ofthe blades being connected to one pair of spokes and the heel ends ofthe blades to the other pair of spokes, said blades being ofsubstantially uniform cross section throughout their length and arrangedwith their concave sides facing rearwardly and having thel edges of eachblade in such a'position that any line taken radially across said edges,will be at substantially right angles to the axis of rotation to preventexcessive centrifugal throw of the air as said air travels along theinclined concave sides of the blade with gradually increasing pressure.

2. A propeller wheel as in claim l in which apair of obliquely disposedbraces have their outer ends connected with the heel-supporting spokesadjacent the inner edge of the respective blade and the inner ends ofsaid braces secured to diametrically opposite sides of the hub at therear of the concave side of the blades for maintaining said bladesagainst forward deflection.

In witness whereof I have hereunto set my hand this 13th da of July1927.

UCIAN M. FOSTER.

